1. Field of the Invention
The present invention relates to cosmetic and dermatological preparations, in particular those of the oil-in-water type, to processes for their preparation and to their use for cosmetic and medicinal purposes.
2. Discussion of Background Information
The human skin is the largest human organ and performs numerous vital functions. Having an average area of about 2 m2 in adults, it has a prominent role as a protective and sensory organ. The purpose of this organ is to transmit and avert mechanical, thermal, actinic, chemical and biological stimuli. In addition, it has an important role as a regulatory and target organ in human metabolism.
The main aim of skincare in the cosmetics sense is to strengthen or restore the skin's natural function as a barrier against environmental influences (e.g. dirt, chemicals, microorganisms) and against the loss of endogenous substances (e.g. water, natural fats, electrolytes), and also to assist its horny layer in its natural regeneration ability in cases of existing damage.
If the barrier properties of the skin are impaired, increased resorption of toxic or allergenic substances or attack by microorganisms may result, leading to toxic or allergic skin reactions.
Another aim of skincare is to compensate for the loss by the skin of sebum and water caused by daily washing. This is particularly important if the natural regeneration ability is inadequate. Furthermore, skincare products should protect against environmental influences, in particular against sun and wind, and delay skin aging.
Medicinal topical compositions usually comprise one or more medicaments in an effective concentration. For the sake of simplicity, in order to clearly distinguish between cosmetic and medicinal use and corresponding products, reference is made to the legal provisions in the Federal Republic of Germany (e.g. Cosmetics Directive, Foods and Drugs Act).
Emulsions are generally understood as meaning heterogeneous systems which consist of two liquids, which are usually referred to as phases, and which are immiscible or miscible with one another only to a limited extent. In an emulsion, one of the two liquids is dispersed in the form of very fine droplets in the other liquid.
If the two liquids are water and oil and oil droplets are very finely dispersed in water, this is an oil-in-water emulsion (O/W emulsion, e.g. milk). The basic character of an O/W emulsion is determined by the water. In the case of a water-in-oil emulsion (W/O emulsion, e.g. butter), the principle is reversed, the basic character being determined here by the oil.
Gel creams are particularly light products with a low emulsifier and lipid content. They are characterized by the fact that they can be readily distributed on the skin and impart a fresh feel. Following product application, no or only a little residue should remain on the skin. Gel creams usually comprise a relatively high content of hydrophilic thickeners (e.g. carbopols, xanthan gum, hydroxyethylcellulose) for thickening and stabilizing the systems. Since the thickener or the thickener system is present in the external phase, it has a significant influence on the sensory properties of the product. Current thickener systems can either not be distributed readily, do not produce a fresh feeling or leave behind an excessively greasy residue on the fingers and/or a harsh, sticky feel on the skin after the product has been distributed on the skin.